(1) Field of the Invention
The present invention relates to a boiler as heat source equipment that transfers heat obtained by combusting fuel to water, and thereby transforms the water to steam or warm water, and particularly to transition control between stages when combustion control is performed in the plurality of combustion stages.
The present application claims the benefit of patent application number 2009-119304, filed in Japan on May 15, 2009, the subject matter of which is hereby incorporated herein by reference.
(2) Description of the Related Art
Conventionally, there has been provided a boiler that includes an air supply device capable of varying a supply amount of combustion air, and a fuel supply device capable of varying a supply amount of fuel, wherein a combustion amount can be controlled in a plurality of combustion states such as high combustion, low combustion, and stop, which is disclosed in Japanese Unexamined Patent Publication No. 2006-145121 and Japanese Unexamined Patent Publication No. 2005-172365, for example.
In this manner, in the boiler that controls the combustion amount in the plurality of combustion stages, a rotational rate of a fan of an air blower in the air supply device is increased or decreased, and an opening of a damper device is changed to thereby supply the combustion air of amounts required in the respective combustion states, and further a proportional control valve is used as a combustion valve, or a plurality of combustion valves are selectively opened and closed to thereby supply the fuel of the amounts required in the respective combustion states.